Two-stroke internal combustion engine

ABSTRACT

A two-stroke engine having a cavity formed by the piston head and subdivided into a first chamber fed with air and a second chamber fed with a mixture of fuel and air.

United States Patent [191 [111 3,921,608 Kottmann Nov. 25, 1975 [54] TWO-STROKE INTERNAL COMBUSTION 1,527,166 2/1925 Bezu 123/67 ENGINE 2,522,649 9/1950 Tenny 123/70 R 2,776,650 1/1957 Zimmermann 123/70 V X [76] Inventor: Helmut Kottmann, 11 Gluckstrasse,

7067 Urbach Germany FOREIGN PATENTS OR APPLICATIONS Filed: p 4 16,865 9 5 mted Kingdom 0 R Appl. No.: 457,166

U.S. Cl. 123/69 R; 123/70 R Int. Cl. F02B 1/08 Field of Search 123/67, 70 R, 70 V, 72,

References Cited UNITED STATES PATENTS 10/1924 Hentschke 123/70 R Primary ExaminerWendel1 E. Burns Assistant Examiner-David D. Reynolds Attorney, Agent, or FirmWi1liam Anthony Drucker [57] ABSTRACT A two-stroke engine having a cavity formed by the piston head and subdivided into a first chamber fed with air and a second chamber fed with a mixture of fuel and air.

8 Claims, 6 Drawing Figures US. Patent Nov. 25, 1975 Sheet10f3 3,921,608

U.S. Patant Nov. 25, 1975 Sheet2of3 3,921,608

US. Patent N0v.25, 1975 Sheet30f3 3,921,608

FIGS

TWO-STROKE INTERNAL COMBUSTION. ENGINE BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to a two-stroke lifting-cylinder combustion engine with a charging pump cylinder parallel or inclined in respect of the working cylinder, the pump piston and the working piston being driven by the crankshaft, the said pump piston being designed as a cylindrical slide piston with an aperture controlling the overflow channel.

2. Description of thePrior Art Ger. Pat. No. 917,645 describes a combustion engine of this kind in which the cylindrical slide piston does not thrust the mixture of fuel and air into the working cylinder until the working piston has already closed the outlet channel. It is true that this measure reliably prevents live gases from entering the outlet channel direct, but their transfer at such a late stage can only be effected with the use of corresponding high pressures. This leads to an undesirable increase in the power consumed in driving the charging pump. Furthermore, partial escape, through the outlet channel, of the scavenging air conveyed by the crank box pump, with the consumption of power, is unavoidable, as is also the uncontrollable mixing of the said air with the'residual gases in the working cylinder.

U.S. Pat. No. 2,522,649 describes a combustion engine of the type mentioned at the beginning, in which the mixture of fuel and air is already thrust from the cylindrical slide piston into the working cylinder when the piston associated with the latter is situated in the zone of its upper dead centre. The transfer operation thus takes place with relative ease. Here again, however, it is not possible to ensure a layered charging operation, i.e., store a richer mixture in that zone of the combustion chamber which is situated in the vicinity of the sparking plug.

SUMMARY OF THE INVENTION The object of this invention is to eliminate this drawback. The preparation and the distribution of the mixture are to be improved. In addition, the live gas charge is to be sharply separated from the residual gases and the scavenging losses are to be reduced to a minimum.

The invention enables this object to be achieved as a result of the fact that the cavity formed by the piston head and the widened part of the nature of a cylindrical slide is subdivided by a separating wall largely parallel to the longitudinal axis of the piston into a first chamber fed with air and a second chamber fed with a mixture of fuel and air, each of these chambers having at least one connecting channel associated with it.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 shows a longitudinal section through an example, with a cylindrical slide piston subdivided into two chambers by a separating wall;

FIG. 2 shows a section along the line IIII of FIG. 1; and

FIGS. 3 and 4 show, on the same lines, a somewhat modified example, as do also FIGS. 5 and 6.

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the example shown in FIG. 1 and 2 the cavity formed by the cylindrical slide part 12 of the pump pis- 2 ton 4 is subdivided into two chambers 21 and 22 by a separating wall 20.

Two overflow apertures 23 and are associated with the chamber 21 and one overflow aperture 11 with the chamber 22. This latter overflow aperture coincides with the connecting channel 9, just as the overflow aperture 23 coincides with the connecting channel 24, when the pump piston 4 is situated in its upper dead centre position. Air is taken in by suction through the inlet channel 7. During the compression of the air, fuel is only injected into the chamber 22, by means of an injection nozzle 27. Consequently, at the end of the precompression stroke of the pump piston 4, a particularly rich mixture of fuel and air flowsout of the chamber 22, through the overflow aperture 11 and through the connecting channel 9, into the working cylinder chamber 1, the direction of entry being mainly orientated to g the combustion chamber 19, while the air pre-compressed in the chamber 21 flows into the working cylinder via the overflow apertures 23 and 25 and via the connecting channels 24 and 26 associated with them. If the overflow apertures 23 and 25 are positioned higher up in the pump piston 4 than the overflow aperture 11, this ensures that the air pre-compressed in the chamber 21 of the pump piston 4 will flow into the working cylinder 1, via the connecting channels 24 and 26, somewhat earlier than the mixture of fuel and air pre compressed in the chamber 22 flows through the connecting channel 9. This measure ensures that the combustion chamber 19 will be' fed with a mixture of fuel and air particularly favourable to ignition.

In the example shown in FIGS. 3 and 4 the pump piston 4 is likewise subdivided into the chambers 21' and 22 by a separating wall 20. This separating wall 20', however, is situated in the direction of the two inlet channels 7 and 7, so that when the pump piston 4 occupies its lower dead centre position air will be taken in by suction through the channel 7 and a mixture of petrol and air through the channel 7 at the same time. As in the machine shown in FIGS. 1 and 2, therefore, a comparatively rich mixture and also air will be precompressed in the charging pump cylinder 2 simultaneously.

In the upper dead centre position air will flow into the working chamber 1 from the chamber 21, via the recess 23 and through the connecting channel 24', while a mixture of fuel and air capable of igniting will flow out of the chamber 22', via the recess 25' and through the connecting channel 26. In this machine likewise it is possible, by positioning the overflow aperture 23' higher up in the pump piston 4, to ensure that the air charge will flow out of the chamber 21' into the working cylinder 1, via the connecting channel 24, somewhat sooner than the mixture of fuel and air flows out of the chamber 22 through the connecting channel 26, in order to obtain a favourable scavenging efficiency. Unlike the machine shown in FIGS. 1 and 2, this machine can also be equipped with a carburettor.

In the example shown in FIGS. 5 and 6 the pump piston 4 is subdivided into the chambers 21" and 22" by a cylindrical separating wall 20. Owing to the pipe 28 extending into the chamber 22" the spacial separation between the two chambers is maintained even when the pump piston 4 is at lower dead centre. Through the inlet channel 30 the chamber 22 is supplied with a mixture of fuel and air via a non-return valve 29.

The chamber 21" is provided with an air charge, as an alternative to the design shown in FIGS. 1 and 2, via

3 a non-return valve 29 and through the inlet channel 31.

The charges are thrust into the working cylinder from the chambers 21 and 22" in the same way as in the example shown in H68. 1 and 2. V

I claim:

1. In a two-stroke-lifting cylinder combustion engine having an engine block; a charging pump cylinder and a working cylinder provided in the said block; a crankshaft; and a cylindrical slide pump piston and a working piston located in said pump cylinder and working cylinder, respectively, and connected to the crankshaft so as to be driven thereby; said block defining an overflow channel therein interconnecting said cylinders, and said pump piston having an aperture therein for controlling the flow of fuel and air through said channel; the improvement comprising a separating wall extending in a direction substantially parallel to the longitudinal axis of the cylindrical slide pump piston and located in the pump piston for subdividing a cavity defined therein into first and second chambers, said block defining channels therein for interconnecting each of the chambers with the working cylinder, wherein air in the first chamber is fed into the working cylinder via one of the channels in said block and a fuel and air mixture in said second chamber is fed into the working cylinder via another of the channels in the block.

2. An engine as claimed in claim 1, wherein the said block defines two channels therein connecting the said first chamber to the. said working cylinder and one channel connecting the said second chamber with said working cylinder, the point of connection of the second chamber channel with said working chamber being lopump cylinder common to both said chambers forthe inflow of air to said chambers and a second inlet channel to said charging pump cylinder for the inflow of fuel into said second chamber.

4. An engine as claimed in claim 1, wherein the block defines therein a first inlet channel into said charging. pump cylinder for the inflow of air into said first.cham-- ber and a second inlet channel into said charging pump cylinder for the inflow of a mixture of air and fuel into the second chamber.

S. An engine as claimed in claim 4, further comprising a pipe extending from said second inlet channel into the second chamber. a

6. An engine as claimed in claim 5, further compris ing a pipe extending from said first inlet channel into said charging pump cylinder so as to project into said first chamber when said pump piston is at a top dead centre position.

7. An engine as claimed in claim 6, further comprising a non-return valve connected with said second inlet channel.

8. An engine as claimed in claim7, further compris 7 ing a non-return valve connected with said first inlet' 

1. In a two-stroke lifting cylinder combustion engine having an engine block; a charging pump cylinder and a working cylinder provided in the said block; a crankshaft; and a cylindrical slide pump piston and a working piston located in said pump cylinder and working cylinder, respectively, and connected to the crankshaft so as to be driven thereby; said block defining an overflow channel therein interconnecting said cylinders, and said pump piston having an aperture therein for controlling the flow of fuel and air through said channel; the improvement comprising a separating wall extending in a direction substantially parallel to the longitudinal axis of the cylindrical slide pump piston and located in the pump piston for subdividing a cavity defined therein into first and second chambers, said block defining channels therein for interconnecting each of the chambers with the working cylinder, wherein air in the first chamber is fed into the working cylinder via one of the channels in said block and a fuel and air mixture in said second chamber is fed into the working cylinder via another of the channels in the block.
 2. An engine as claimed in claim 1, wherein the said block defines two channels therein connecting the said first chamber to the said working cylinder and one channel connecting the said second chamber with said working cylinder, the point of connection of the second chamber channel with said working chamber being located above the points of connection of said first chamber channels with said working chamber relative to the direction of movement of said working piston from bottom dead centre to top dead centre.
 3. An engine as claimed in claim 1, wherein said block defines therein one inlet channel to said charging pump cylinder common to both said chambers for the inflow of air to said chambers and a second inlet channel to said charging pump cylinder for the inflow of fuel into said second chamber.
 4. An engine as claimed in claim 1, wherein the block defines therein a first inlet channel into said charging pump cylinder for the inflow of air into said first chamber and a second inlet channel into said charging pump cylinder for the inflow of a mixture of air and fuel into the second chamber.
 5. An engine as claimed in claim 4, further comprising a pipe extending from said second inlet channel into the second chamber.
 6. An engine as claimed in claim 5, further comprising a pipe extending from said first inlet channel into said charging pump cylinder so as to project into said first chamber when said pump piston is at a top dead centre position.
 7. An engine as claimed in claim 6, further comprising a non-return valve connected with said second inlet channel.
 8. An engine as claimed in claim 7, further comprising a non-return valve connected with said first inlet channel. 